Biocidal compositions and use thereof containing a synergistic mixture of N-tributyl tetradecyl phosphonium chloride and B-bromo-B-nitrostyrene

ABSTRACT

A bactericidal composition and method for inhibiting and controlling the growth of the capsulated, facultative bacterium, Klebsiella pneumoniae, are disclosed. The composition comprises an amount, effective for the intended purpose of n-tributyl tetradecyl phosphonium chloride (TPC) and B-bromo-B-nitrostyrene (BNS). The method comprises administering between about 0.1 to about 200 parts of this combined treatment (based on one million parts of the desired aqueous system) to the particular water containing system for which treatment is desired.

BACKGROUND OF THE INVENTION

The formation of slimes by microorganisms is a problem that isencountered in many aqueous systems. For example, the problem is notonly found in natural waters such as lagoons, lakes, ponds, etc., andconfined waters as in pools, but also in such industrial systems ascooling water systems, air washer systems and pulp and paper millsystems. All possess conditions which are conducive to the growth andreproduction of slime-forming microorganisms. In both once-through andrecirculating cooling systems, for example, which employ largequantities of water as a cooling medium, the formation of slime bymicroorganisms is an extensive and constant problem.

Airborne organisms are readily entrained in the water from coolingtowers and find this warm medium an ideal environment for growth andmultiplication. Aerobic and heliotropic organisms fluorish on the towerproper while other organisms colonize and grow in such areas as thetower sump and the piping and passages of the cooling system. The slimeformation not only aids in the deterioration of the tower structure inthe case of wooden towers, but also promotes corrosion when it depositson metal surfaces. Slime carried through the cooling system plugs andfouls lines, valves, strainers, etc., and deposits on heat exchangesurfaces. In the latter case, the impedance of heat transfer can greatlyreduce the efficiency of the cooling system.

In pulp and paper mill systems, slime formed by microorganisms iscommonly encountered and causes fouling, plugging, or corrosion of thesystem. The slime also becomes entrained in the paper produced to causebreakouts on the paper machines, which results in work stoppages and theloss of production time. The slime is also responsible for unsightlyblemishes in the final product, which result in rejects and wastedoutput.

The previously discussed problems have resulted in the extensiveutilization of biocides in cooling water and pulp and paper millsystems. Materials which have enjoyed widespread use in suchapplications include chlorine, chlorinated phenols, organo-bromines, andvarious organo-sulfur compounds. All of these compounds are generallyuseful for this purpose but each is attended by a variety ofimpediments. For example, chlorination is limited both by its specifictoxicity for slime-forming organisms at economic levels and by thetendency of chlorine to react, which results in the expenditure of thechlorine before its full biocidal function is achieved. Other biocidesare attended by odor problems and hazards with respect to storage, useor handling which limit their utility. To date, no one compound or typeof compound has achieved a clearly established predominance with respectto the applications discussed. Likewise, lagoons, ponds, lakes, and evenpools, either used for pleasure purposes or used for industrial purposesfor the disposal and storage of industrial wastes, become, during thewarm weather, besieged by slime due to microorganism growth andreproduction. In the case of industrial storage or disposal ofindustrial materials, the microorganisms cause additional problems whichmust be eliminated prior to the materials' use or disposal of the waste.

Naturally, economy is a major consideration with respect to all of thesebiocides. Such economic considerations attach to both the cost of thebiocide and the expense of its application. The cost performance indexof any biocide is derived from the basic cost of the material, itseffectiveness per unit of weight, the duration of its biocidal orbiostatic effect in the system treated, and the ease and frequency ofits addition to the system treated. To date, none of the commerciallyavailable biocides has exhibited a prolonged biocidal effect. Instead,their effectiveness is rapidly reduced as a result of exposure tophysical conditions such as temperature, association with ingredientscontained by the system toward which they exhibit an affinity orsubstantivity, etc., with a resultant restriction or elimination oftheir biocidal effectiveness, or by dilution.

As a consequence, the use of such biocides involves their continuous orfrequent addition to systems to be treated and their addition tomultiple points or zones in the systems to be treated. Accordingly, thecost of the biocide and the labor cost of applying it are considerable.In other instances, the difficulty of access to the zone in which slimeformation is experienced precludes the effective use of a biocide. Forexample, if in a particular system there is no access to an area atwhich slime formation occurs the biocide can only be applied at a pointwhich is upstream in the flow system. However, the physical or chemicalconditions, e.g., chemical reactivity, thermal degradation, etc., whichexist between the point at which the biocide may be added to the systemand the point at which its biocidal effect is desired render theeffective use of a biocide impossible.

Similarly, in a system experiencing relatively slow flow, such as apaper mill, if a biocide is added at the beginning of the system, itsbiocidal effect may be completely dissipated before it has reached allof the points at which this effect is desired or required. As aconsequence, the biocide must be added at multiple points, and even thena diminishing biocidal effect will be experienced between one point ofaddition to the system and the next point downstream at which thebiocides may be added. In addition to the increased cost of utilizingand maintaining multiple feed points, gross ineconomies with respect tothe cost of the biocide are experienced. Specifically, at each point ofaddition, an excess of the biocide is added to the system in order tocompensate for that portion of the biocide which will be expended inreacting with other constituents present in the system or experiencephysical changes which impair its biocidal activity.

SUMMARY OF THE INVENTION

The biocidal compositions of the present invention comprise, as activeingredients, 1) n-tributyl tetradecyl phosphonium chloride (TPC) and 2)B-bromo-B-nitrostyrene (BNS).

PRIOR ART

TPC is commercially available from Ciba-Geigy under the trademark"Belclene 350" and is marketed as a "broad spectrum biocide specificallydeveloped for the control of microbiological fouling in cooling watersystems." Use of the TPC compound in a biological composition isdisclosed in U.S. Pat. Nos. 4,725,587 and 4,835,144 (Whitekettle etal.), and U.S. Pat. No. 4,835,143 (Donofrio et al.) of common assignmentherewith.

B-bromo-B-nitrostyrene is commercially available from the GivaudanCorporation.

The synergistic effect obtained by combining TPC and BNS has not beenpreviously disclosed.

DETAILED DESCRIPTION OF THE INVENTION

Surprisingly, the present inventors have found that mixtures of TPC andBNS are especially efficacious in controlling the growth of bacterialmicrobes, specifically the Klebsiella pneumoniae species. Thisparticular species is a member of the capsulated, facultative class ofbacteria and is generally present in air, water and soil. These bacteriacontinually contaminate open cooling systems and pulping and papermakingsystems and are among the most common slime formers. The slime may beviewed as being a mass of agglomerated cells stuck together by thecementing action of the gelatinous polysaccharide or proteinaceoussecretions around each cell. The slimy mass entraps other debris,restricts water flow and heat transfer, and may serve as a site forcorrosion.

The fact that the Klebsiella species used in the tests is a facultativespecies is important as, by definition, such bacteria may thrive undereither aerobic or anaerobic conditions. Accordingly, by reason ofdemonstrated efficacy in the growth inhibition of this particularspecies, one can expect similar growth inhibition attributes when otheraerobic or anaerobic bacterial species are encountered. It is alsoexpected that these compositions will exhibit similar growth inhibitionattributes when fungi and algae species are encountered.

As noted above, TPC is available from Ciba-Geigy and is sold under thetrademark "Belclene 350". The physical properties of "Belclene 350" arereported as being:

    ______________________________________                                        Appearance         Clear, colorless liquid                                    Specific Gravity at 20° C.                                                                0.96                                                       pH                 7.0-8.0                                                    Boiling Point      100° C.                                             Freezing Point     -8 to -10° C.                                       Viscosity          50-80 cP                                                   Odor               Slight                                                     Solubility Water   Completely miscible in                                                        all proportions                                            Methanol           Greater than 50%                                           Isopropanol        Greater than 50%                                           Ethylene Glycol    Greater than 50%                                           ______________________________________                                    

In accordance with the present invention, the combined TPC and BNStreatment may be added to the desired aqueous system in need of biocidaltreatment, in an amount of from about 0.1 to about 200 parts of thecombined treatment to one million parts (by weight) of the aqueousmedium. Preferably, about 5 to about 50 parts of the combined treatmentper one million parts (by weight) of the aqueous medium is added.

The combined treatment is added, for example, to cooling water systems,paper and pulp mill systems, pools, ponds, lagoons, lakes, etc., tocontrol the formation of bacterial microorganisms, which may becontained by, or which may become entrained in, the system to betreated. It has been found that the compositions and methods ofutilization of the treatment are efficacious in controlling thefacultative bacterium, Klebsiella pneumoniae, which may populate thesesystems. It is thought that the combined treatment composition andmethod of the present invention will also be efficacious in inhibitingand controlling all types of aerobic and anaerobic bacteria.

Surprisingly, it has been found that when the ingredients are mixed, incertain instances, the resulting mixtures possess a higher degree ofbactericidal activity than that of the individual ingredients comprisingthe mixture. Accordingly, it is possible to produce a highly efficaciousbactericide. Because of the enhanced activity of the mixture, the totalquantity of the bacterial treatment may be reduced. In addition, thehigh degree of bactericidal effectiveness which is provided by each ofthe ingredients may be exploited without use of higher concentrations ofeach.

The following experimental data were developed. It is to be rememberedthat the following examples are to be regarded solely as beingillustrative, and not as restricting the scope of the invention.

DESCRIPTION OF PREFERRED EMBODIMENT

TPC and BNS were added in varying ratios and over a wide range ofconcentrations to a liquid nutrient medium which was subsequentlyinoculated with a standard volume of a suspension of the facultativebacterium Klebsiella pneumoniae. Growth was measured by determining theamount of radioactivity accumulated by the cells when 14C-glucose wasadded as the sole source of carbon in the nutrient medium. The effect ofthe biocide chemicals, alone and in combination, is to reduce the rateand amount of 14C incorporation into the cells during incubation, ascompared to controls not treated with the chemicals. Additions of thebiocides, alone and in varying combinations and concentrations, weremade according to the accepted "checkerboard" technique described by M.T. Kelley and J. M. Matsen, Antimicrobial Agents and Chemotherapy. 9:440 (1976). Following a two hour incubation, the amount of radioactivityincorporated in the cells was determined by counting (14C liquidscintillation procedures) for all treated and untreated samples. Thepercent reduction of each treated sample was calculated from therelationship: ##EQU1##

Plotting the % reduction of 14C level against the concentration of eachbiocide acting alone results in a dose-response curve, from which thebiocide dose necessary to achieve any given % reduction can beinterpolated.

Synergism was determined by the method of calculation described by F. C.Kull, P. C. Eisman, H. D. Sylwestrowicz and R. L. Mayer, AppliedMicrobiology 9,538 (1961) using the relationship: ##EQU2## where: Q_(a)=quantity of compound A, acting alone, producing an end point

Q_(b) =quantity of compound B, acting alone, producing an end point

Q_(A) =quantity of compound A in mixture, producing an end point

Q_(B) =quantity of compound B in mixture, producing an end point

The end point used in the calculations is the % reduction caused by eachmixture of A and B. ^(Q) A and ^(Q) B are the individual concentrationsin the A/B mixture causing a given % reduction. ^(Q) a and ^(Q) b aredetermined by interpolation from the respective dose-response curves ofA and B as those concentrations of A and B acting alone which producethe same % reduction as each specific mixture produced.

Dose-response curves for each active acting alone were determined bylinear regression analysis of the dose-response data. Data were fittedto a curve represented by the equation shown with each data set. Afterlinearizing the data, the contributions of each biocide component in thebiocide mixtures to the inhibition of radioisotope uptake weredetermined by interpolation with the dose-response curve of therespective biocide. If, for example, quantities of ^(Q) A plus ^(Q) Bare sufficient to give a 50% reduction in 14C content, ^(Q) a and ^(Q) bare those quantities of A or B acting alone, respectively, found to give50% reduction in 14C content. A synergism index (SI) is calculated foreach combination of A and B.

Where the SI is less than 1, synergism exists. Where the SI=1,additivity exists. Where the SI is greater than 1, antagonism exists.

The data in the following tables come from treating Klebsiellapneumoniae, a common nuisance bacterial type found in industrial coolingwaters and in pulping and paper making systems, with varying ratios andconcentrations of TPC and BNS. Shown for each combination is the %reduction of 14C content (% I), the calculated SI, and the weight ratioof TPC and BNS.

                  TABLE I                                                         ______________________________________                                        TPC vs BNS                                                                    ppm      ppm      Ratio                                                       TPC.sup.1                                                                              BNS.sup.2                                                                              TPC:BNS      % I  SI                                        ______________________________________                                         0       40         0:100      95                                              0       20         0:100      92                                              0       10         0:100      89                                              0        5         0:100      36                                              0         2.5      0:100       0                                              0          1.25    0:100       0                                             100       0       100:0        97                                             80        0       100:0        86                                             50        0       100:0        73                                             40        0       100:0        49                                             25        0       100:0        34                                             20        0       100:0         5                                             100      40       2.5:1        99   2.73                                      100      20        5.1         99   1.90                                      100      10       10:1         99   1.48                                      100       5       20:1         99   1.27                                      100        2.5    40:1         98   1.19                                      100         1.25  80:1         98   1.14                                      80       40        2:1         99   2.52                                      80       20        4:1         99   1.68                                      80       10        8:1         99   1.27                                      80        5       16.1         98   1.08                                      80         2.5    32:1         97   0.99                                      80          1.25  64:1         95   0.98                                      50       40       1.25:1       99   2.20                                      50       20       2.5:1        99   1.37                                      50       10        5:1         99   0.95                                      50        5       10:1         97   1.10                                      50         2.5    20:1         94    0.70*                                    50          1.25  40:1         89    0.70*                                    40       40        1:1         99   2.09                                      40       20        2:1         99   1.26                                      40       10        4:1         98    0.85*                                    40        5        8:1         96    0.67*                                    40         2.5    16:1         90    0.63*                                    40          1.25  32:1         76    0.73*                                    25       40         1:1.6      99   1.93                                      25       20       1.25:1       99   1.10                                      25       10       2.5:1        98    0.70*                                    25        5        5:1         96    0.50*                                    25         2.5    10:1         84    0.49*                                    25          1.25  20:1         68    0.57*                                    20       40        1:2         99   1.88                                      20       20        1:1         98   1.05                                      20       10        2:1         97    0.65*                                    20        5        4:1         93    0.48*                                    20         2.5     8:1         73    0.52*                                    20          1.25  16:1         53    0.64*                                    ______________________________________                                         .sup.1 product containing 50% actives TPC                                     .sup.2 product containing 95% actives BNS                                

                  TABLE II                                                        ______________________________________                                        TPC vs BNS                                                                    ppm      ppm      Ratio                                                       TPC.sup.1                                                                              BNS.sup.2                                                                              TPC:BNS      % I  SI                                        ______________________________________                                         0       40         0:100      95                                              0       20         0:100      92                                              0       10         0:100      89                                              0        5         0:100      53                                              0         2.5      0:100       0                                              0          1.25    0:100       0                                             100       0       100:0        95                                             80        0       100:0        92                                             50        0       100:0        66                                             40        0       100:0        64                                             25        0       100:0        24                                             20        0       100:0        16                                             100      40       2.5:1        99   2.88                                      100      20        5.1         99   1.97                                      100      10       10:1         99   1.53                                      100       5       20:1         99   1.30                                      100        2.5    40:1         97   1.23                                      100         1.25  80:1         98   1.14                                      80       40        2:1         99   2.66                                      80       20        4:1         99   1.76                                      80       10        8:1         99   1.31                                      80        5       16.1         98   1.10                                      80          2.5   32:1         98   0.98                                      80          1.25  64:1         96   0.97                                      50       40       1.25:1       99   2.23                                      50       20       2.5:1        99   1.44                                      50       10        5:1         99   0.99                                      50        5       10:1         97    0.79*                                    50         2.5    20:1         93    0.73*                                    50          1.25  40:1         85    0.77*                                    40       40        1:1         99   2.23                                      40       20        2:1         99   1.33                                      40       10        4:1         98    0.90*                                    40        5        8:1         97    0.68*                                    40         2.5    16:1         90    0.65*                                    40          1.25  32:1         81    0.68*                                    25       40         1:1.6      99   2.07                                      25       20       1.25:1       98   1.19                                      25       10       2.5:1        97    0.75*                                    25        5        5:1         94    0.55*                                    25         2.5    10:1         78    0.58*                                    25          1.25  20:1         63    0.66*                                    20       40        1:2         99   2.02                                      20       20        1:1         98   1.14                                      20       10        2:1         97    0.69*                                    20        5        4:1         88    0.56*                                    20         2.5     8:1         77    0.51*                                    20          1.25  16:1         61    0.58*                                    ______________________________________                                         .sup.1 product containing 50% actives TPC                                     .sup.2 product containing 95% actives BNS                                     Asterisks in the SI column indicate synergistic combinations in accordanc     with the Kull method supra.                                              

In Tables I and II, differences seen between the replicates are due tonormal experimental variance.

In accordance with Tables I-II supra., unexpected results occurred morefrequently within the product ratios of "Belclene 350" to BNS of fromabout 40:1 to 2:1. Since the "Belclene 350" product contains about 50%active biocidal component (i.e., tri n-butyl tetradecyl phosphoniumchloride) and the BNS product contains about 95% active biocidalcomponent, when based on the active biocidal component unexpectedresults appear more frequently within the range of active component of"Belclene 350": BNS of about 20:1 to 1:1. At present, it is mostpreferred that any commercial product embodying the invention comprisesa weight ratio of active component of about 2:1 TPC:BNS.

While this invention has been described with respect to particularembodiments thereof, it is apparent that numerous other forms andmodifications of this invention will be obvious to those skilled in theart. The appended claims and this invention generally should beconstrued to cover all such obvious forms and modifications which arewithin the true spirit and scope of the present invention.

We claim:
 1. A bacterial inhibiting composition comprising a synergisticmixture of (a) n-tributyl tetradecyl phosphonium chloride and (b)B-bromo-B-nitrostyrene wherein the weight ratio of (a):(b) is from about20:1 to 1:1.
 2. The composition as recited in claim 1 wherein the weightratio of (a) to (b) is about 2:1.
 3. A method for controlling the growthof Klebsiella pneumoniae bacteria in an aqueous system which comprisesadding to said system from about 0.1 to 200 parts per weight of acomposition per one million parts per weight of said aqueous system,said composition comprising a synergistic mixture of (a) n-tributyltetradecyl phosphonium chloride and (b) B-bromo-B-nitrostyrene, theweight ratio of (a) to (b) being from about 20:1 to 1:1.
 4. The methodas recited in claim 3 wherein the weight ratio of (a):(b) is about 2:1.5. The method as recited in claim 3 wherein said composition is added tosaid system in an amount of from about 5 to about 50 parts per millionof said aqueous system.
 6. The method as recited in claim 3 wherein saidaqueous system comprises a cooling water system.
 7. The method asrecited in claim 3 wherein said aqueous system comprises a pulping andpapermaking system.